1. Field of the Invention
The present invention relates to an image forming apparatus, an reading apparatus, and a control method of reading, and in particular to a technique for reading an image on a sheet on which the image is formed, with no waste and with required image quality.
2. Description of Related Art
An reading apparatus is connected on the rear stage of an image forming apparatus for forming an image on a sheet, and constitutes an image forming system. In this image forming system, it is possible to read the image on an sheet on which the image is formed, by the reading apparatus.
In such an image forming system, by referring to the result of reading of the formed image, it is possible to adjust an image forming position, to adjust an image quality, to find a sheet having an inappropriately formed image, to store the image as an evidence of the output of the formed image (image for confirming evidence), and the like.
As such techniques, related inventions are proposed in patent documents including Japanese Laid-Open Patent Application Publication No. 2005-223381 and Japanese Laid-Open Patent Application Publication No. 2004-20650.
In Japanese Laid-Open Patent Application Publication No. 2005-223381, a technique is proposed in which when forming images on both sides, positioning is performed by reading an image-formed sheet with a line sensor and referring to the result of reading.
In Japanese Laid-Open Patent Application Publication No. 2004-20650, a technique is proposed in which a sheet on which a defective image is formed is detected as a defective sheet, and the defective sheet is rejected from output objects by reading an image-formed sheet with an line sensor and referring to the result of the reading.
In addition, besides the above-mentioned patent documents, there is a technique in which an image of each sheet are all stored as evidence so that sheets having images formed thereon were output.
However, no consideration is given about what resolution and gradation to use in the case that the above-mentioned different intended uses simultaneously exist. In other words, it is a common practice in the image forming system that images are read with the same resolution and the same gradation even for different intended uses.
Thus, when the setting is made to satisfy the resolution required for positioning and the gradation required for density adjustment, the reading quality is excessively high for an intended use of an image for confirming evidence. That is to say, the data volume becomes unnecessarily large, and the data may a big burden when storing the data.
On the other hand, when the resolution or gradation is lowered in consideration of the efficiency of storing data, a new problem arises in which positioning are density adjustment cannot be performed with high accuracy.
The image forming apparatus for production print has high image quality, and the apparatus requires high resolution data for positioning. On the other hand, the image forming apparatus for production print has high productivity and performs a large amount of image forming. As a result, the image for confirming evidence needs to store data of many pages.
In other words, the image forming apparatus for production print needs to store data of multiple pages with high resolution. Thus, the data volume produced by reading is increased, and a problem arises in which the data becomes a big burden when storing the data.
An object of the present invention is to realize an image forming apparatus, a reading apparatus, and a control method of reading in which an image on the sheet being discharged with the image formed thereon can be read with no waste and with required image quality.